Peptidic oxytocin receptor agonists include the natural hormone oxytocin, and carbetocin.

Oxytocin is a potent uterotonic agent, clinically used to induce labour, and has been shown to enhance the onset and maintenance of lactation, Gimpl, G. et al., Physiol. Rev. 81 (2001) 629-683 and Ruis H. et al., British Medical Journal 283 (1981) 340-342. Carbetocin (1-deamino-1-carba-2-tyrosine(O-methyl)-oxytocin) is also a potent uterotonic agent clinically used for the control of uterine atony and excessive bleeding. Further research indicates that oxytocin agonists are useful for the treatment of inflammation and pain, including abdominal and back pain; sexual dysfunction, both male and female; irritable bowel syndrome (IBS), constipation and gastrointestinal obstruction; autism, stress, anxiety (including anxiety disorder) and depression (Pitman R. et al., Psychiatry Research, 48:107-117; Kirsch P et al., The Journal of Neuroscience, 25(49):11489-11493); surgical blood loss, the control of post-partum haemorrhage, wound healing and infection; mastitis and placenta delivery; and osteoporosis. Additionally, oxytocin agonists may be useful for the diagnosis of both cancer and placental insufficiency.
A disadvantage of both oxytocin and carbetocin are their lack of selectivity over the vasopressin receptors, especially the V2 receptor. During administration of oxytocin this disadvantage is observed by such side effects as antidiuresis and hyponatremia.
In order to improve the pharmacological properties of oxytocin, analogues of oxytocin have been synthesised. Such analogues are described by Grozonka Z. et al. in J. Med. Chem. 26 (1983) 555-559 and J. Med. Chem. 26 (1983) 1786-1787, and by Engstrøm T. et al. in E. J. Pharmacol. 355 (1998) 203-210. Additionally, oxytocin analogues with antagonist activity at the oxytocin receptor have been described by Fragiadaki M. et al. in E. J. Med. Chem. (2007) 799-806.
The present invention may provide selective, efficacious compounds, providing feasible alternatives and/or improvements e.g. in the treatment of compromised lactation conditions.